Question: The Gregorian calendar is based on what and is the main regulatory text for who?
Paraphrase: What is the Gregorian calendar based on and who is the main regulatory text for?
SPARQL (Wikidata): SELECT ?ans_1 ?ans_2 WHERE { wd:Q12138 wdt:P92 ?ans_1 . wd:Q12138 wdt:P144 ?ans_2 }
Answer: Inter gravissimas, Julian calendar